U Joint Breaking, Please HELP

I have a 74' Bronco and keep breaking the u joint where the drive shaft enters the rear end. It is a single u joint. In four months, I've had to replace four. The last one was the heavier duty u joint spicer u joint. It lasted less than 200 miles and seen very few mud holes. I can tell you that the bronco has had a 2" lift (spacers). The angle/pitch from drive shaft to rear end yoke is not a problem. In fact, it looks like there is no more than 1-2 degrees of angle. My bronco will allow up to 15 degree angle. I assume the rear end was shifted upward to correct the pitch when the spacers was installed. Looking at the drive shaft from the rear of the bronco, it looks like it is running straight. When weather warms a little, I'm going to measure from frame to center of drive shaft at one end of drive shaft and do the same for other end of drive shaft to make sure they are equal. The rear end has a mini spool installed.

Can anyone suggest possible problems or better ideals on how to check if drive shaft is running straight from frame.

Oh, I have been greasing u joint after installing.

Thanks

Hi 407.,

With all due respect., you left out one important ingredient...THE DRIVER..! >

"it looks like there is no more than 1-2 degrees of angle."

1-3 deg. is good...it should NOT be 0 deg.

"My bronco will allow up to 15 degree angle."

I doubt this..! /emoticons/[email protected] 2x" width="20" height="20" />

From the factory the "weak point" is "traction" ....when you increase traction (lockers), you move the "weak point."

The new weak point is axles & U-joints. It's poss. the axles were up-graded during the installation of the spool. (You didn't say.)

Point being you can't "****-bent for leather", hammer the throttle 'cause things will break with a "TAD" in there. b-(

If you're, in fact, easy with the throttle ... then something else is amiss..

"how to check if drive shaft is running straight from frame"

If you mean "parallel" with frame., this is not necessary.

HTH.,

B

Check the pinion yoke on the rear end for wear. Had the same prblems on a 66 Mustang. A new yoke from Currie solved it. And be sure you have the correct-size u-joint. JSM84

everything that just shoot me and bully bob is true. if the yoke is messed up then it wont support the joint properly, and u joints are not designed to run strait on, they will fail if they dont have some angle to them. and one other thing, make sure you do not overtorque the u bolts on the u joint caps this causes undue stress also.

How to I check to see how much angle there is? After reading reply's to my question, It sounds like I may be overtightened the u joint to the yoke. Also, my buddy and I thought that one side of the yoke sticks out a little more than the other. Luckily, I have another used yoke that came off a bronco. I'll correct both of these problems and see if it fixes. Thanks for all the suggestions.

I have one last question. When I have to replace u joint, I have to take whole driveshaft out. Will the slip yoke not slide off the driveshaft? I've tried by loosening and pulling on slip yoke but it will not come off.

Well there it is...!!

The slip joint should move in & out several inches on the splines, easily.

(allowing for serv. to 1 u-joint while leaving the other end in place)

Sounds like it's frozen/jammed all the way extended.

This would cause many problems incl. snapping U-joints.

Could be the wrong length dr. shaft if, while sitting static., it's fully extended.

will the slip joint slide completely off the drive shaft?

Yep..., in most cases.

My new one has a *****-on seal cover..I've not attemped to seperate so it may need to be un-screwed B/4 it will seperate.

I have unscrewed it but still couldn't get it to come completely off. I guess I need to brake out the hammer. I would make changing Ujoints much easier.

You never said if it moves in and out at all...?

Don't know if a hammer is a good idea....??

Yes, it moves in and out. Even has a grease fitting which I keep greased. I figure if you loosen the nut, it should slide all the way off but I can not get it to slide completely off. Would be much easier to slide off and be able to put in vise rather than having to take both ends of the driveshaft loose to get in vise.

Ok.., things are becoming more clear.....

1)If the 1st. time you changed the u-joint., you cleaned & polished the two holes the u-joint caps slide into.... you shouldn't need to remove shaft & put it in a vice.

Should be able to swap out a rear u-joint in 10-20 min. fr. under the veh.

2)This isn't something you'll be doing often once the prob. is found.

3)With the "splined slip-joint" functioning properly...it should be at, or close to, "center-of-stroke" when installed on veh. & at rest.

4)u-joints need to match the yokes they're going into.....Dana/Cleveland, Spicer., etc.

Other than that, we're back to "square one" & unless someone else chimes in with an idea., you'll likely need to stop at your local drive-line shop & have them spot :-B the problem.

P.S. don't clamp that slip-shaft in a metal vice..... [-X

you have to use a press or a vise to change my rear u joint also because it is pressed into the yoke on the shaft and has u bolts on the rear end. is the slip yoke in the center of travel?